Modeling, control and power management of hybrid photovoltaic fuel cells with battery bank supplying electric vehicle

Modeling, control and power management of hybrid photovoltaic fuel cells with battery bank supplying electric vehicle

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Modeling, control and power management of hybrid photovoltaic fuel cells with battery bank supplying electric vehicle Zahra Mokrani, Djamila Rekioua, Toufik Rekioua* Laboratoire LTII, Universite de Bejaia, 06000 Bejaia, Algeria

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abstract

Article history:

In this paper, modeling, control and power management (PM) of hybrid Photovoltaic Fuel

Received 22 February 2014

cell/Battery bank system supplying electric vehicle is presented. The HPS is used to pro-

Received in revised form

duce energy without interruption. It consists of a photovoltaic generator (PV), a proton

26 March 2014

exchange membrane fuel cell (PEMFC), and a battery bank supplying an electric vehicle of

Accepted 27 March 2014

3 kW. In our work, PV and PEMFC systems work in parallel via DC/DC converter and the

Available online xxx

battery bank is used to store the excess of energy. The mathematical model topology and it power management of HPS with battery bank system supplying electric vehicle (EV) are the

Keywords:

significant contribution of this paper. Obtained results under Matlab/Simulink and some

Hybrid power system

experimental ones are presented and discussed.

Photovoltaic

Copyright ª 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Fuel cells Battery Power management Electric vehicle

Introduction Hybrid power systems are used to supply loads and ensure load demand without interruption. We can use different sources, conventional ones as coal, natural gazes, fossils fuels,. or renewables ones as solar, wind, hydraulic,. [1e13]. In addition to energy, a hybrid system may also include a DC or AC converters, a storage system, and a control system for power management. All these components can be connected in different architectures. The electric vehicle in the automotive field is the cleanest and most environmentally friendly transport solution. Also, it overcomes the noise since there is almost none noise. In fact, an electric car is really ecological if the electrical energy consumed is produced from renewable energy sources as solar, wind, hydro,.. However, these

renewable sources are intermittent, why a storage system must be inserted. Generally we use batteries. Electric vehicles with batteries already exist and are have autonomy less than 200 km. These last years, manufacturers are interested to hydrogen or fuel cell vehicle which can have autonomy of 400e800 km depending on car models, and which produces less carbon dioxide (g/km). A fuel cell works as a battery. It stores energy but as hydrogen. It react hydrogen with the oxygen in the air to obtain water and energy. However, extracting hydrogen from air or water requires twice as much energy as the use of battery in electric vehicle, thus the cost of hydrogen production is high. It will be interesting to use another source of energy as solar. The present work is dedicated to a study of hybrid photovoltaic/Fuel Cells system supplying an electric vehicle with battery bank. The advantages of each source used, allow us to obtain

* Corresponding author. E-mail addresses: [email protected], [email protected] (T. Rekioua). http://dx.doi.org/10.1016/j.ijhydene.2014.03.215 0360-3199/Copyright ª 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Please cite this article in press as: Mokrani Z, et al., Modeling, control and power management of hybrid photovoltaic fuel cells with battery bank supplying electric vehicle, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/ j.ijhydene.2014.03.215

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Nomenclature Af Cd C10 Eb ENerst Fr fro Ftire G Ipv Iph Ish Isc I0 Impp K m nb Pmpp PPV q r Rb Rs Rsh Tj Tjref TPEMFC Uact

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frontal surface area of the vehicle, m aerodynamic drag coefficient rated capacity, A h voltage source, V voltage Nerst, V total force, N m rolling resistance force constant rolling resistance force, N m solar radiation, W/m2 output-terminal current, A diode-current, A shunt-leakage current, A short circuit current, A saturation current of the diode, A maximum current at PPM, A Boltzmann constant, J/K vehicle total mass, kg number of cells maximum power point, W photovoltaic power, W electron charge, C tire radius, m internal resistance, U series resistance, U shunt resistance, U temperature cells, K reference temperature of the PV cell, K absolute operating temperature of the stack, K activation overvoltage, V

a cheaper and less polluting EV. We use in our case an induction motor (IM) of 3 kW as propulsion of the EV. To kept the DC bus voltage at a constant value when the speed of the rotor varies, different control techniques can be used as stator oriented control (SFOC), rotor flux oriented control (RFOC), Direct Torque Control (DTC), Fuzzy logic controller (FLC),.. In our work, the IM

Uconc Uohm V Vmpp Voc VPEMFC

concentration or diffusion over-voltage, V resistive or ohmic over-voltage, V vehicle speed, m/s maximum voltage at PPM, V open circuit voltage, V fuel cell voltage, V

Greek letters temperature coefficient of short-current, A/K asc constants ai b road slope angle,  boc voltage temperature coefficient, V/K DT heating of the accumulator, K air density rair Abbreviations AC alternate current DC direct current DTC direct Torque control EV electric vehicle FC fuel cell FLC fuzzy logic controller HPS hybrid power system IM induction motor MPP maximum power point PEMFC proton exchange membrane fuel cell PM power management PV photovoltaic panels RFOC rotor flux oriented control SFOC stator oriented control

is controlled using DTC Strategy, which is a powerful control method for motor drives. The global system is presented, modeled and simulated under Matlab/Simulink. Each subsystem has been simulated separately, and then, the power management of the proposed system is given. Obtained simulation results and some experimental ones are presented and discussed.

Fig. 1 e Studied hybrid photovoltaic/fuel cells/battery bank for electric vehicle. Please cite this article in press as: Mokrani Z, et al., Modeling, control and power management of hybrid photovoltaic fuel cells with battery bank supplying electric vehicle, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/ j.ijhydene.2014.03.215

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Table 1 e Parameter of the PV panel Siemens SM110-24 [1]. PPV Impp Vmpp Isc Voc asc boc Pmpp

Fig. 2 e Different forces acting on a vehicle moving along a slope.

Photovoltaic power (W) Maximum current at PPM (A) Maximum voltage at PPM (V) Short circuit current (A) Open circuit voltage (V) Temperature coefficient of short-current (A/K) Voltage temperature coefficient (V/K) Maximum power point (W)

110 W 3.15 A 35 V 3.45 A 43.5 V 1.4 mA/ C 152 mV/ C 110 W

We have three forces: - Rolling resistance force Ftire due to the friction of the vehicle tires on the road. It is given as: Ftire ¼ m  g  fro

(1)

with: m is the vehicle total mass, g is the gravity acceleration, fro is the rolling resistance force constant.

Fig. 3 e Equivalent circuit of photovoltaic cell.

- Aerodynamic drag force Faero caused by the friction on the body moving through the air. Its expression is: Faero ¼ ð1=2Þ  rair  Af  Cd  V2

Studied system The global system consists of a photovoltaic generator, a proton exchange membrane fuel cell and a battery bank supplying an electric vehicle of 3 kW (Fig. 1).

(2)

with: rair is the air density, Af is the frontal surface area of the vehicle, Cd is the aerodynamic drag coefficient, V is the vehicle speed. - Climbing force Fslope which depends on the road slope. Fslope ¼ m  g  sinðbÞ

(3)

with: b is the road slope angle. The total resistive force Fr is given as:

Electric vehicle description The different forces acting on an EV with m total mass moving along a slope are represented in Fig. 2.

Fr ¼ Ftire þ Faero þ Fslope

(4)

Fig. 4 e Bloc diagram of photovoltaic module. Please cite this article in press as: Mokrani Z, et al., Modeling, control and power management of hybrid photovoltaic fuel cells with battery bank supplying electric vehicle, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/ j.ijhydene.2014.03.215

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Fig. 5 e Electrical characteristics under experimental and simulation.

The load torque can be written as: Tr ¼ Fr  r

(5)

with: r is the tire radius, Fr is the total force.

The bloc diagram of PV module can be represented as (Fig. 4): The parameters of the solar module used (Siemens SM11024) are given in Table 1. The electrical characteristics IpveVpv and PpveVpv are given in Fig. 5 [1].

Modeling of the studied system Modeling of fuel cell PEMFC

Modeling of photovoltaic panels The model studied in this work consists of a single diode for the cell polarization function and two resistors for the losses (Fig. 3).where: Ipv is the output-terminal current, Iph is the light-generated current, Id is the diode-current, Ish is the shunt-leakage current, Rs is the series resistance and represents the internal resistance to the current flows, and depends on the p-n junction depth, the impurities and the contact resistance, Rsh is the shunt resistance and it is inversely related with leakage current to the ground, G solar radiation (W/m2). The Ipv(Vpv) characteristic of this model is given by [1,4,9,13]: Ipv ¼ Iph  Id  IRsh

(6)

The electrical representation is as follows (Fig. 6).

Fig. 7 e Battery equivalent circuit.

     q  Vpv þ Rs  Ipv Vpv þ Rs  Ipv Ipv ¼ Iph  I0  exp 1  A  Ns  K  Tj Rsh (7)

Fig. 6 e Electrical representation of a PEMFC.

Fig. 8 e Stator flux trajectory by appropriate voltage vectors selection.

Please cite this article in press as: Mokrani Z, et al., Modeling, control and power management of hybrid photovoltaic fuel cells with battery bank supplying electric vehicle, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/ j.ijhydene.2014.03.215

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Fig. 9 e DTC general configuration.

The cell voltage VPEMFC is given as the summation of Nerst voltage ENerst due to various irreversible loss mechanisms, activation overvoltage Uact, concentration or diffusion overvoltage Uconc and resistive or ohmic over-voltage Uohm [1,4,8]. VPEMFC ¼ ENernst þ Uact  Uohm  Uconc where:

(8)

ENernst ¼ a1 þ a2  ðTPEMFC  298:15Þ þ a3   TPEMFC  0:5  ln PO2 þ ln PH2   Uact ¼ b1 þ b2  TPEMFC þ b3  TPEMFC  ln j  5  103 þ b4  TPEMFC  ln CO2

(9)

(10)

Fig. 10 e Block diagram of the overall system. Please cite this article in press as: Mokrani Z, et al., Modeling, control and power management of hybrid photovoltaic fuel cells with battery bank supplying electric vehicle, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/ j.ijhydene.2014.03.215

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Uohm

   0 1  T 2 IPEMFC 2:5 181:6  1 þ 0:03  IPEMFC  þ 0:06  S S 303 cell cell Ipac B C i h   IPEMFC þ Scell  Rc A ¼ @ T303 Scell exp 4:18 l  0:634  3  IPEMFC Scell T

with C O2 is the oxygen concentration in the cathode area (mol/cm3), bi are constants, Scell: Area active cell (m2), Rc: equivalent contact resistance of the electrodes conduction (U).   j Uconc ¼ B  ln 1  jmax

Battery modeling The model used in this work is based on the electrical scheme given in Fig. 7. We have: Ubatt ¼ nb  Eb  nb  Rbatt  Ibatt

(13)

where: Eb the voltage source, Rb, an internal resistance, nb number of cells. The battery capacity Cbatt is given as [1]: 1:67  ð1 þ 0:005  DTÞ  0:9 1 þ 0:67  I10I

(14)

where: DT is the heating of the accumulator, C10 is the rated capacity (I10). The state of battery charge can be written as: SOC ¼ 1 

Ibatt Vbattdischarge ¼ nb  ½1:965 þ 0:12  SOC  nb  C10 " # 4 0:27  þ þ 0:002  ð1  0:007$DTÞ SOC1:5 1 þ I1:3 batt (18)

(12)

with: TPEMFC: absolute operating temperature of the stack (K), ai are constants.

Cbatt ¼ C10 

(11)

Direct torque control strategy In principle, direct torque control (D.T.C) strategy is based on instantaneous space vector theory. By optimal selection of the space voltage vectors in each sampling period, this method archives effective control of the stator flux and torque. The stator flux can be estimated using measured current and voltage vectors [14e17]: Zt fs ðtÞ ¼

ðVs  Rs  is Þ  dt

The stator flux components fsa and fsb along a and b stator axes can be estimated as: Zt fsa ðtÞ ¼

ðVsa  Rs  isa Þ  dt 0

(20)

Zt fsb ðtÞ ¼

Q Cbatt

(19)

0

(15)

ðVsb  Rs  isb Þ  dt 0

The magnitude of the stator flux can then be estimated by:

with: Q ¼ Ibatt  t

(16)

where: t is the discharging time with a current Ibatt. The battery voltage (charge and discharge) is function of the internal components of the battery. It is written as: Vbattcharge ¼ nb  ½2 þ 0:16  SOC þ nb # " Ibatt 6 0:27  þ þ 0:002  ð1  0:007$DTÞ SOC1:5 C10 1 þ I1:3 batt (17)

fs ¼

qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi f2sa þ f2sb

(21)

And the electromagnetic torque can be calculated by: Te ¼

  3  p  fsa  isb  fsb  isa 2

(22)

Fig. 8 shows the voltage vectors which are usually employed in DTC scheme [16]. A simplified block diagram of direct torque control is shown in Fig. 9.

Table 3 e Parameters of the induction machine. Parameters

Table 2 e Parameters of the electric vehicle model. Parameters Vehicle total mass Rolling resistance force constant Air density Frontal surface area of the vehicle Tire radius Aerodynamic drag coefficient

Symbol

Values

m fr rair Af R Cd

1300 0.01 1.20 2.60 0.32 0.32

Units kg kg m2 m2 m

Shaft power Number of pole pairs Stator resistance Rotor resistance Mutual inductance Stator(rotor) self-inductance Inertia moment Viscous friction

Symbols

Values

Pu P Rs Rr M Ls ¼ Lr J f

3 2 1.76 1.95 0.183 0.194 0.02 0.0001

Units kW U U H H

kg m2 N m s2

Please cite this article in press as: Mokrani Z, et al., Modeling, control and power management of hybrid photovoltaic fuel cells with battery bank supplying electric vehicle, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/ j.ijhydene.2014.03.215

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Fig. 11 e Power and vehicle speed.

Power management of the studied system EV using batteries storage must be recharged regularly. Those using fuel cells for feeding electrical energy, a supply for hydrogen is necessary. And those equipped with PV panels, solar energy provides them energy only during sunshine period. Generally, EV uses batteries for storage, but due to the less autonomy, hydrogen or fuel cell vehicle, solar vehicle or a combination of solar, FC and battery bank can be a competitive solution. Power management control is necessary to make coordination between the different energy sources. In our work, we choose to use the battery bank system to starts producing energy. Then Hydrogen is used by the fuel cell to produce energy and at least photovoltaic system works to convert irradiation to electrical energy provided to a DC bus. The total power is calculated as [9,10,17]: Pload ¼ Pbatt þ PFC þ Ppv

(23)

The bloc diagram of the overall studied system under Matlab/Simulink is given (Fig. 10). The motor and electric vehicle parameters used in simulation are listed respectively in Tables 2 and 3.

The power and vehicle speed are given as follow (Fig. 11). The obtained results are presented in Fig. 12(a, b, c, d, e). We can note from the obtained results, that the proposed hybrid system works as proposed by the power management control. To test the robustness of DTC, we make a sudden variation of rotational speed at t ¼ 2 s (Figs. 13e18). The obtained results confirm the presented theory. We note that even the rotation speed of the induction motor changes, the flux kept constant.

Conclusion In this paper, modeling, control and power management of hybrid Photovoltaic/Fuel cells/Battery bank system supplying an electric vehicle is presented. The different parts of the proposed system have been firstly simulated separately and then the power management control has been used to coordinate between the three sources to supply the EV. The simulation model of the hybrid system has been developed using MATLAB/Simulink. The obtained results show the feasibility of the hybrid system production for an electric vehicle.

Please cite this article in press as: Mokrani Z, et al., Modeling, control and power management of hybrid photovoltaic fuel cells with battery bank supplying electric vehicle, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/ j.ijhydene.2014.03.215

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Fig. 12 e (a) Power delivered by photovoltaic generator; (b) Power delivered by battery bank; (c) Power delivered by fuel cells; (d) Power delivered to the load by the three sources.

Please cite this article in press as: Mokrani Z, et al., Modeling, control and power management of hybrid photovoltaic fuel cells with battery bank supplying electric vehicle, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/ j.ijhydene.2014.03.215

Fig. 13 e Rotor speed waveform.

Fig. 14 e Stator current waveform.

Fig. 15 e Zoom on stator current waveform.

Fig. 16 e Electromagnetic torque waveform. Please cite this article in press as: Mokrani Z, et al., Modeling, control and power management of hybrid photovoltaic fuel cells with battery bank supplying electric vehicle, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/ j.ijhydene.2014.03.215

Fig. 17 e Zoom on electromagnetic torque waveform.

Fig. 18 e Stator flux circular trajectory.

references

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[7] Abou El-Maaty Metwally Metwally Aly Abd El-Aal. Modelling and simulation of a photovoltaic fuel cell hybrid system [A dissertation for the degree of doctor in engineering (Dr.Ing.)]. Faculty of electrical Engineering, University of Kassel; April 15, 2005. [8] Bettar N. Study and modeling of a PEM fuel cell [Master’s thesis]. Algeria: University of Bejaia; 2008. [9] Chekired F, Larbes C, Rekioua D, Haddad F. Implementation of a MPPT fuzzy controller for photovoltaic systems on FPGA circuit. Energy Procedia 2011;6:541e9. [10] Wang C, Nehrir MH. Power management of a stand-alone wind/photovoltaic/fuel cell energy system. IEEE Trans Energy Convers 2008;23:957e67. [11] Ipsakis D, Voutetakis S, Seferlis P, Stergiopoulos F, Elmasides C. Power management strategies for a standalone power system using renewable energy sources and hydrogen storage. Int J Hydrogen Energy 2009;34(16):7081e95. [12] Keliang Z, Ferreira JA, De Haan SWH. Optimal energy management strategy and system sizing method for standalone photovoltaic-hydrogen systems. Int J Hydrogen Energy 2008;33(2):477e89. [13] Lalouni S, Rekioua D. Modeling and simulation of a photovoltaic system using fuzzy logic controller. In: Proceedings e international conference on developments in eSystems Engineering, DeSE 2009, 23e28; 2009. [14] Rekioua T, Rekioua D. Direct torque control strategy of permanent magnet synchronous machines. In: 2003 IEEE Bologna PowerTech e conference proceedings, 2; 2003. pp. 861e6. [15] Abdelli R, Rekioua D, Rekioua T, Tounzi A. Improved direct torque control of an induction generator used in a wind conversion system connected to the grid. ISA Trans 2013;52(4):525e38. [16] Rekioua D, Rekioua T. DSP-controlled direct torque control of induction machines based on modulated hysteresis control. In: Proceedings of the international conference on microelectronics, ICM; 2009. pp. 378e81. [17] Garcı´a P, Torreglosa JP, Ferna´ndez LM, Jurado F. Optimal energy management system for stand-alone wind turbine/ photovoltaic/hydrogen/battery hybrid system with supervisory control based on fuzzy logic. Int J Hydrogen Energy 2013;38(33):14146e58.

Please cite this article in press as: Mokrani Z, et al., Modeling, control and power management of hybrid photovoltaic fuel cells with battery bank supplying electric vehicle, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/ j.ijhydene.2014.03.215